This invention relates generally to engine-driven, electrical generators, and in particular, to a generator structure incorporating a variable pitch sheave arrangement for facilitating the cooling of a radiator of an engine-driven, electrical generator.
Engine-driven, electrical generators are used in a wide variety of applications. Typically, such electrical generators utilize a single driving engine directly coupled to a generator or alternator through a common shaft. Upon actuation of the engine, the crankshaft thereof rotates the common shaft so as to drive the alternator which, in turn, generates electricity. It can be appreciated that since the engine and the alternator are housed in a single enclosure, a significant amount of heat is generated within the enclosure during operation of the electrical generator.
Heretofore, in order to cool the components of a prior electrical generator, louvers were provided in the walls of the enclosure thereof. A fan, coupled to the crankshaft of the engine, rotates during operation of the electrical generator. The rotating fan draws air into the enclosure through the louvers in the walls and blows air over the components of the electrical generator, including the engine, the alternator, and the radiator. In such a manner, it is intended that the air passing over the components of the electrical generator have a cooling effect on the components during their operation such that the temperatures of the components are maintained below safe operating limits.
While functional under certain conditions, air flow arrangements of prior electrical generators have significant limitations. Typically, the fan used to cool the radiator is rotated at a predetermined, constant speed. It can be appreciated that during start-up of the electrical generator, the temperature of the engine coolant flowing through the radiator is at a minimum. As such, it is unnecessary to rotate the fan at full speed in order to cool the engine coolant flowing through the radiator. As the engine of the electrical generator approaches full operating speed, the temperature of the engine coolant flowing through the radiator increases. Consequently, it becomes necessary for the rotational speed of the engine fan to increase in order for the engine fan to adequately cool the engine coolant flowing through the radiator. As such, it is highly desirable to provide a fan drive structure which provides greater cooling of the radiator as the temperature of the coolant flowing therethrough increases.
Therefore, it is a primary object and feature of the present invention to provide a fan drive system for an electrical generator structure which improves the overall operating efficiency of the same.
It is a further object and feature of the present invention to provide a fan drive system for an electrical generator structure which more economically cools the radiator of the generator structure than prior fan drive systems.
It is a still further object and feature of the present invention to provide a fan drive system for an electrical generator structure which is simple to operate and inexpensive to implement.
In accordance with the present invention, a variable pitch drive sheave is provided for interconnecting first and second fan pulleys operatively connected to a fan by a rotatable fan shaft and first and second rotatable drive pulleys. The fan generates an air flow through a radiator to cool the temperature thereof. The variable pitch drive sheave assembly includes a shaft extending along an axis and having first and second opposite ends. A first outer sheave member is positioned adjacent the first end of the shaft and a second outer sheave member is positioned adjacent the second end of the shaft. An intermediate sheave member is positioned between the first and second ends of the shaft. A first movable sheave member is slidably supported on the shaft between the first outer sheave member and the intermediate sheave member. The first movable sheave member and the outer sheave member defining a first drive pulley groove therebetween for receiving a first drive belt. The first movable sheave member and the intermediate sheave member define a first fan pulley groove therebetween for receiving a first fan belt. The second movable sheave member is slidably supported on the shaft between the second outer sheave member and the intermediate sheave member. The second movable sheave and the second outer sheave member define a second drive pulley groove therebetween for receiving a second drive belt. The second movable sheave member and the intermediate sheave member define a second fan pulley groove therebetween for receiving a second fan belt. The first drive belt operatively connects the first drive pulley groove and the first drive pulley. The second drive belt operatively connects the second drive pulley groove and the second drive pulley. The first fan belt operatively connects the first fan pulley groove and the first fan pulley. The second fan belt operatively connects the second fan pulley groove and the second fan pulley. As described, rotation of the first and second drive pulleys is translated to the first and second fan pulleys.
The drive sheave assembly may include an actuator operatively connected to the shaft for moving the first and second movable sheave members between a first high speed position and a second low speed position. The first and second drive pulley grooves have a first depth when the first and second movable sheave members are in the high speed position and a second depth with the first and second movable sheave members in the low speed position. The first depth of the first and second drive pulleys is greater than the second depth of the first and second drive pulleys. In addition, the first and second fan pulley grooves have a first depth when the first and second movable sheave members are in the high speed position and a second depth when the first and second movable sheave members are in the low speed position. The first depth of the first and second fan pulleys grooves is less than the second depth of the first and second fan pulley grooves. It is contemplated to provide a monitoring device for monitoring the temperature of the radiator. The monitoring device controls movement of the actuator in response to the temperature of the radiator.
In accordance with a further aspect of the present invention, a fan drive arrangement is provided. The fan drive arrangement operatively connects a drive shaft to a fan mounted on a rotatable fan shaft. The fan drive arrangement includes first and second fan pulleys interconnected to the fan shaft. Each drive pulley has a groove therein for receiving a corresponding fan belt. First and second drive pulleys are interconnected to the drive shaft. Each fan pulley has a groove therein for receiving a corresponding drive belt. A variable pitch sheave assembly is also provided. The variable pitch sheave assembly is movable between a first high speed position and a second low speed position and includes a rotatable sheave shaft having first and second opposite ends. A first outer member is fixed to the first end of the sheave shaft and a second outer member is fixed to the second end of the sheave shaft. An intermediate member is fixed to the sheave shaft between the first and second ends thereof. A first slidable member slides along the sheave shaft between the first outer member and the intermediate member. The first slidable member and the first outer member define a first drive pulley therebetween and the first slidable member and intermediate member define a first fan groove therebetween. A second slidable member is slidable along the sheave shaft between the intermediate member and a second outer member. The second slidable member and the second outer member define a second drive groove therebetween and the second slidable member and the intermediate member define a second fan groove therebetween. A first drive belt is seated in the groove in the first drive pulley and in the first drive groove to translate rotation of the first drive pulley to the variable pitch sheave assembly. A second drive belt is seated in the groove in the second drive pulley and the second drive groove to translate rotation of the second drive pulley to the variable pitch sheave assembly. A first fan belt is seated in the first fan groove and the groove in the first fan pulley to transfer rotation of the variable pitch sheave assembly to the first fan pulley. A second fan belt is seated in the second fan groove and the groove in the second fan pulley to translate rotation of the variable pitch sheave assembly to the second fan pulley.
The first and second drive grooves have a first depth with the variable pitch sheave assembly in the high speed position and a second depth with the variable speed pitch assembly in the low speed position. The first depth of the first and second drive grooves is greater than the second depth of the first and second drive fan grooves. The first and second fan grooves also have a first depth with the variable pitch sheave assembly in the high speed position and a second depth with the variable pitch sheave assembly in the low speed position. The first depth of the first and second fan grooves is less than the second depth of the first and second fan grooves.
An actuator is operatively connected to the variable pitch sheave assembly for moving the variable pitch sheave assembly between the high speed position and a low speed position. A controller is operatively connected to the actuator. The controller monitors the temperature of the radiator and controls operation of the actuator in response to the temperature monitored.
In accordance with a further aspect of the present invention, a method is provided of cooling the engine coolant flowing through a radiator. The method includes the step of monitoring a temperature of coolant flowing through the radiator. A fan is positioned adjacent to the radiator and rotates at a predetermined speed. The speed of the fan is varied in response to the temperature of the coolant.
The method includes the additional steps of supporting the fan on a rotatable fan shaft and a driven pulley attached thereto. The driven fan pulley includes a groove formed therein. A drive pulley is also provided. The drive pulley has a groove formed therein which has a predetermined depth. A fan belt is positioned about the groove of the driven fan pulley and the groove of the drive pulley such that rotation of the drive pulley is translated to the fan pulley by the fan belt. The step of varying the speed of the fan includes the additional step of varying the depth of the groove in the drive pulley. The depth of the groove in the drive pulley is decreased to increase the speed of the fan and the depth of the groove in the drive pulley is increased to decrease the speed of the fan.
In accordance with a still further aspect of the present invention, a fan drive arrangement is provided. The fan drive arrangement operatively connects a drive shaft to a fan mounted on a rotatable fan shaft. The fan drive arrangement includes first and second fan pulleys interconnected to the fan shaft. Each fan pulley has a groove therein for receiving a corresponding fan belt. First and second drive pulleys are interconnected to the drive shaft. Each drive pulley has a groove therein for receiving a corresponding drive belt. A variable pitch sheave assembly is movable between a first high speed position and a second low speed position. The variable pitch sheave assembly includes first and second drive belt grooves and first and second fan belt grooves. The drive belt grooves have a first depth with variable pitch assembly in the high speed position and a second depth with the variable pitch assembly in the low speed position. The fan belt grooves have a first depth with variable pitch assembly in the high speed position and the second depth with the variable pitch sheave assembly in the low speed position. First and second drive belts are seated in corresponding drive belt grooves in the variable pitch sheave assembly and in corresponding grooves in the drive pulleys to translate rotation of the drive pulleys to the variable pitch sheave assembly. First and second fan belts are seated in corresponding fan belt grooves in the variable pitch sheave assembly and in corresponding grooves in the fan pulleys to translate rotation of the variable pitch sheave assembly to the fan pulleys.
The variable pitch sheave assembly of the fan drive arrangement includes a rotatable sheave shaft having first and second opposite ends. A first outer member is affixed to the first end of the sheave shaft and a second outer member is fixed to the second end of the sheave shaft. An intermediate member is fixed to the sheave shaft between the first and second ends thereof. A first slidable member is slidable along the sheave shaft between the first outer member and the intermediate member. The first slidable member and the first outer member define the first drive belt groove therebetween. The first slidable member and the intermediate member define the first fan belt groove therebetween. A second slidable member is slidable along the sheave shaft between the intermediate member and the second outer member. The second slidable member and the second outer member define the second drive groove therebetween. The second slidable member and the intermediate member define a second fan belt groove therebetween.
The first depth of a drive belt grooves is greater than the second depth of the drive belt grooves. On the other hand, the first depth of the fan belt grooves is less than the second depth of the fan belt grooves. An actuator is operatively connected to the variable pitch sheave assembly for moving the variable pitch sheave assembly between the high speed position and the low speed position. A controller is operatively connected to the actuator and monitors the temperature of the radiator. The controller controls operation of the actuator in response to the temperature of the radiator.